VARIABILITY OF POLLEN TOLERANCE TO LOW-TEMPERATURES IN TOMATO AND RELATED WILD-SPECIES

The poor viability of tomato (Lycopersicon esculentum Mill.) pollen formed at 10 degrees C, or below, strongly decreases fruit set. We evaluated both pollen fertility and pollen shedding produced at minimum temperatures of 10 degrees C or less, by respectively the number of seeds produced by artificial pollinations and the number of sampling dates in which plants released pollen from the anthers, in a total of 170 accessions of Lycopersicon species: L. esculentum (112), L. pimpinellifolium (Jusl.) Mill. (14), L. parviflorum Rick, Kes., Fob. and Holle (5), L. chmielewskii Rick, Kes., Fob. and Holle (1), L. chilense Dun. (3), L. hirsutum Humb. and Bonpl. (12), L. peruvianum (L.) Mill. (21), and L. pennellii (Corr.) D'Arcy (2). In L. esculentum, low temperatures affected pollen fertility negatively, and only 'Mex-69', 'N-709','Mex-72', 'C-20','Stupicke Rane', 'Mex-92', 'Mex-102' and several other cultivars showed a partial pollen cold-tolerance level. The responses of the L. pimpinellifolium and L. chilense accessions were very similar to those of L. esculentum. L. parviflorum and L. chmielewskii accessions were moderately tolerant while L. hirsutum, L. peruvianum, and L. pennellii accessions generally produced fertile pollen below 10 degrees C. The most interesting accessions of these three species were 'PE-37', 'PE-39', 'PE-41', and 'LA 1777' (L. hirsutum); 'T-55', 'PI-251311', 'PI-126448', 'PI-126441', 'PE-20', and 'PE-18' (L. peruvianum); and 'PE-45' and 'PE-47' (L. pennellii). While, in general, tomato cultivars had poor release of pollen, the accessions of wild species with fertile pollen at low temperatures shed pollen satisfactorily. The close association between pollen shedding and pollen fertility below 10 degrees C should facilitate the incorporation of both characters into L. esculentum.